The European Standard EN 751 specifies requirements and test methods for Sealing materials for metallic threaded joints in contact with 1st, 2nd and 3rd family gases and hot water.
The European Norm EN 751 consists of three parts.
EN 751-1: Anaerobe adhesives
EN 751-2: Non-hardening jointing compounds
EN 751-3: Unsintered PTFE tapes